Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$233.57	12.395%	$262.521	$262.52	$262.50	$262.50
Purchase #2	$56.58	12.160%	$63.4601	$63.46	$63.45	$63.50
Purchase #3	$246.46	11.646%	$275.1627	$275.16	$275.15	$275.20
Purchase #4	$48.77	13.653%	$55.4286	$55.43	$55.45	$55.40
Purchase #5	$52.89	5.617%	$55.8608	$55.86	$55.85	$55.90
Purchase #6	$130.77	13.621%	$148.5822	$148.58	$148.60	$148.60
Purchase #7	$87.27	10.470%	$96.4072	$96.41	$96.40	$96.40
7 purchase totals =	$856.31		$957.4226	$957.42	$957.40	$957.50